Wireline is a method of lowering specialised equipment into an oil or gas well, or raising specialised equipment from an oil or gas well. The principle of wireline is to attach a workstring or toolstring to the end of a reel of wire and by reeling out the wire the toolstring is lowered into the well. By either reeling in or reeling out the wire, the toolstring can be made to perform simple tasks downhole. The toolstring consists of a variable combination of individual tools connected together to form a working unit.
Originally, the individual tools were connected together by having co-operating threads provided on the end of each tool so that the tools could be screwed together and tightened using wrenches.
However, recently quick-locking connectors have been provided in which a male member having diametrically opposite flanges is inserted into a female member and rotated relative to the female member so that the flanges co-operate with recesses within the female member to lock the male member to the female member. Rotation of the male member relative to the female member is then prevented by means of a latch which is displaceable in a direction parallel to the longitudinal axis of the toolstring. The latch is mounted in the female member and engages with a slot in the male member to prevent the male and female members rotating after they have been connected together. This axially displaceable latch mechanism comprises a helical spring which acts in the longitudinal axial direction to force the latch member into engagement with the slot in the male member.
However, there are a number of disadvantages with this system. In particular, when the wireline is used for jarring operations the latch member tends to disengage from the slot in the male member due to the high longitudinal axial forces during jarring operations. This can result in rotation of the male member relative to the female member in a downhole situation, which could result in loss of one or more of the tools downhole.
In addition, these type of connectors have a tendency to rock about the diametric axis of the flanges which results in premature wear of the connector and possible failure of the connector.